Conveyors

ABSTRACT

A conveyor having a belt and continuous bearing elements near the lateral edges of the belt to support the belt, in which there is means to supply fluid under pressure to the gaps between the bearing elements and the belt to form a fluid bearing for the belt. The bearing elements may have convex surfaces, and the belt may have cooperating concave surfaces of very slightly smaller concavity, whereby the gaps are narrowest at the edges of the bearing elements. Preferably, the bearing elements are hollow and there is means to supply pressurized fluid to the hollow elements, and thence to the gaps between the bearing elements and the belt.

United States Patent [56] References Cited UNITED STATES PATENTS 756,6004/1904 Dodge 198/184 X 2,066,206 I 2/1936 Laurie 198/184 PrimaryExaminer-Edward A. Sroka Attorney-W. A. Shira, Jr.

ABSTRACT: A conveyor having a belt and continuous bearing elements nearthe lateral edges of the belt to support the belt, in which there ismeans to supply fluid under pressure to the gaps between the bearingelements and the belt to form a fluid bearing for the belt- The bearing;elements may have convex surfaces, and the belt may have cooperatingconcave surfaces of very slightly smaller concavity, whereby the gapsare narrowest at the edges of the bearing elements. Preferably, thebearing elements are hollow and there is means to supply pressurizedfluid to the hollow elements, and thence to the gaps between the bearingelements and the belt.

PATENTED JUL20 IHYI 3,593,839

sum 2 UF 2 CONVEYORS This invention relates to conveyors.

The invention provides a conveyor having a belt which is relativelyrigid laterally and relatively flexible in its direction of travel, andcontinuous bearing elements at or near the lateral edges of the belt tosupport the belt, in which there is means to supply fluid under pressureto the gaps between the bearing elements and the belt to form a fluidbearing for the belt According to a feature of the invention the bearingelements have convex surfaces, and the belt has cooperating concavesurfaces of very slightly smaller concavity, whereby the gaps arenarrowest at the edges of the bearing elements.

In a preferred form the bearing elements are hollow and there is meansto supply pressurized fluid to the hollow elements, and thence to thegaps between the bearing elements and the belt.

In this form it is preferred that there are channels under the hollowelements to catch fluid emitted from the gaps, and there is provisionfor that fluid to be retumed to the fluid supply means.

According to a feature of the invention the fluid is supplied to thegaps through a multiplicity of capillaries or orifices formed or insetin material adjacent to the gaps.

According to a feature of the invention the bearing elements provide orform structural members upholding the belt.

In one preferred form of the invention the material of the belt orbearing elements at the edges of the gaps is flexible so to provide orform a seal. I

According to another feature of the invention fluid emitted from thegaps serves to eject foreign material from between the belt and thebearing elements.

It may be preferred that there is a heater or series of heaters toresist the freezing of the fluid in the gaps.

A specific embodiment of the invention will now be described by way ofexample with reference to the accompanying drawings of which:

FIG. 1 is a lateral section across a conveyor,

FIG. 2 is a sectional view in FIG. 1,

FIG. 3 is a view corresponding to FIG. 2 and showing a variant thereof,

FIG. 4 is a sectional view in side elevation of the end of a conveyor,and

FIG. 5 is a section on the line 55 in FIG. 4.

As shown in FIG. 1, a conveyor belt 10, which is stiff laterally andflexible longitudinally has downwardly concave edges 11 and 12. Alongthe edges of the conveyor there are tubes 13 and 14 supported atintervals on the framework of the conveyor, and the edges of theconveyor rest on the tubes. The tubes are supplied with a pressurizedfluid (such as air, water or oil) which is allowed to escape throughcapillaries or orifices spaced apart along the tops of the tubes. Thecapillaries 15 may be made by forming suitably fine holes at an acuteangle in the tube wall as shown in FIG. 2 or may be separate assemblies16 fitted in holes 17 as indicated in FIG. 3. Altematively fine orificesmay be provided in the tube wall. The capillaries or orifices are placedat intervals along the tube so that preferably there are between two andI2 outlets per foot of tube. The tube may be of any material.

Along the underside of each edge 11 and 12 there is moulded a rubberbearing strip containing a concave portion substantially of the sameradius as the bearing tube. Fluid losses may be reduced by making theradius of this bearing strip slightly less than that of the tube. Theare formed by the concave portion of the rubber-bearing strip will havean included angle preferably between 120 and l80.

When a liquid lubricant (such as oil or water) is used, channels l8 and19 are placed under the tubes 13 and 14 to collect the escaping liquidand to return it to a reservoir, arranged to feed the means topressurize the liquid.

The method of operation is as follows: Pressurized fluid flows along thetubes 13 and 14 and up the capillaries or through the orifices so toexert a pressure on the underside of the conveyor edges 11 and 12thereby forcing the conveyor upwards. This creates or increases gapsbetween the edges of the bearing strips and the tubes and allows thelubricant to escape. The conveyor, therefore, is riding on a fluid filmbetween each of its edges 11 and 17. and the tubes 13 and 14respectively.

The pressure drop in the fluid flowing through the capillaries ororifices is proportional to the flow rate and consequently the pressureunder the bearing strips is inversely proportional to the flow rate.

When the belt is lightly loaded there is a maximum clearance between itand the tube and most of the pressure drop occurs in the capillaries ororifices. When the belt is heavily loaded the clearance is minimal andflow rate is low. Therefore, most of the pressure drop occurs betweenthe outlets from the tube and the extremities of the bearing strip.However, because the pressure drop for a constant volume flow rate isinversely proportional to the cube of the film thickness, the geometryof the bearing ensures that it is only at the extremity of the bearingstrip that an appreciable pressure drop occurs, because it is there thatthe film thickness is a minimum. This effect will be accentuated bydeflection of the rubber in the areas of high pressure (i.e. on top ofthe tube).

The use of a bearing such as has been described in this specificembodiment of the invention has among others the following advantages.

The power consumed in pumping the fluid and in driving the conveyor beltto overcome the viscous resistance is considerably less than the powerconsumed in overcoming for instance the rolling friction resistance ofrollers which might be employed to support the conveyor be1t.

The bearing tube forms the means of delivering the lubricant, thebearing surface, and a rigid edge support for the belt, thereby savingon the cost of an alternative structure which might be needed, such asrollers.

Features of the invention illustrated in the above description of thespecific embodiment include the use of the tube in its triple function,the use of a hydrostatic bearing as described with one of the bearingsurfaces being flexible, and the use of hydrostatic bearings to supportthe edges of a laterally stiff conveyor belt.

FIGS. 4 and 5 show the end of a conveyor-belt arrangement, and in theseFigures an end drum for the conveyor is designated as 20. The end drum20 is supported on a pair of pillars 21 upstanding from a floor 22.There are further pillars 23 and 24 upstanding from the floor of whichpillars 23 can be seen in the sectional view in FIG. 5.

The end drum 20 is driven by a chain 25 which is in turn driven by adrive wheel 26.

The conveyor passing round the drum shown in FIGS. 4 and 5 is of thetype illustrated in FIG. 1, and the conveyor belt, here designated 27has longitudinally running grooves 28 which engage with a safety comb 29at the end of the conveyor and generally above the end drum 20.

Supported on the pillars 23 and 24 there are relatively rigid tubes 31and 32 of circular cross section. These tubes 31 and 32 are disposedbeneath the edge portions of the conveyor and form bearing elementstherefor. The tubes are of the type shown in detail in FIG. 2 or FIG. 3,and underneath the tubes there are channels 33 and 34 which gather fluidemitted from the gaps between the conveyor and "the tubes 31 and 32. Thechannels are drained by drain pipes 35 and 36 which lead back through acommon pipe 37 to a reservoir 38. A pump 39 draws fluid from thereservoir and pumps this fluid under pressure through a pipe 41 to theinterior of the tubes 31 and 32.

After passing over the end drum 20 the return run portion of theconveyor passes over idler rollers'42 and 43 supported between thepillars 23 and the pillars 24 respectively.

In operation fluid is pumped to the tubes 31 and 32 by the pump 39, andis emitted from the tubes through the convex external surfaces thereof.The fluid is trapped in the gap between the edges of the conveyor andthe convex external surfaces of the bearing elements, so to form a fluidbearing. The edges of the concave portion of the conveyor belt whichsurround the surface emitting the liquid may be flexible, and it is afeature of the invention that the radius of curvature of the concavesurface on the underside of the conveyor belt is very slightly less thanthe radius of curvature of the tubes 31 and 32. Heaters in or under thetubes 31 and 32 may delay freezing of the fluid therein and in normalcircumstances the belt will be supported on a fluid trapped in the gapsbetween the tube and the belt. The conveyor is drawn along by the actionof the end drum 20 and there are at the ends of the channels 33 and 34dams which stop leakage of fluid as the fluid is emitted from the end ofthe interface.

The tubes 31 and 32 may be of plastics material, but can conveniently bemade of steel so that the tubes form the main supportfor the conveyorbelt. The tubes are rigidly attached to the pillars 23 and 24.

1 claim:

1. A conveyor comprising a belt which is relatively rigid laterally andrelatively flexible in its direction of travel, laterally spacedsupporting surfaces on the inner face of said belt adjacent the edgesthereof, and laterally spaced continuous bearing elements near thelateral edges of the belt cooperating with said surfaces on the belt tosupport the latter only adjacent its edges, and means to supply fluidunder pressure to the gaps between the bearing elements and the belt toform a fluid bearing for the belt.

2. A conveyor as claimed in claim 1 in which the bearing elements haveconvex surfaces, and the said supporting surfaces on the belt havecooperating concave surfaces of very slightly smaller concavity, wherebythe gaps are narrowest at the edges of the bearing elements.

3. A conveyor as claimed in claim 1 in which the bearing elements arehollow and there is means to supply pressurized fluid to the hollowelements, and thence to the gaps between the bearing elements and thebelt.

4. A conveyor as claimed in claim 3 in which there are channels underthe hollow elements to catch fluid emitted from the gaps, and there isprovision for that fluid to be returned to the fluid supply means.

5. A conveyor as claimed in claim 1, in which the fluid is supplied tothe gaps through a multiplicity of capillaries inset in materialadjacent the gaps.

6. A conveyor as claimed in claim 1, in which the fluid is supplied tothe gaps through a multiplicity of orifices formed in material adjacentthe gaps.

7. A conveyor as claimed in claim 1 in which the bearing elements formstructural members upholding the belt.

8. A conveyor as claimed in claim 1 in which the material of one of thebelt and bearing elements at the edges of the gaps is flexible so toform a seal.

9. A conveyor as claimed in claim 1 in which fluid emitted from the gapsserves to eject foreign material from between the belt and the bearingelements.

Patent No. Dated July 20, 1971 Inventor(!) Edward Peter Smith It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 1, line #3, after "View" insert ---along the line II-II---;Column 2, line 66, before "conveyor" insert ---edges of the--.

Signed and sealed this 25th day of January 1972.

(SEAL) Attast:

EDWARD M.FLETCHER,JR. ROBERT HALK Attesting Officer i ner of PatentsFORM PC4050 (10-69) T USCOMM-DC 60376-P69 US GOVERNMENT PRINTING OFFICE959 0-35$'33l

1. A conveyor comprising a belt which is relatively rigid laterally andrelatively flexible in its direction of travel, laterally spacedsupporting surfaces on the inner face of said belt adjacent the edgesthereof, and laterally spaced continuous bearing elements near thelateral edges of the belt cooperating with said surfaces on the belt tosupport the latter only adjacent its edges, and means to supply fluidunder pressure to the gaps between the bearing elements and the belt toform a fluid bearing for the belt.
 2. A conveyor as claimed in claim 1in which the bearing elements have convex surfaces, and the saidsupporting surfaces on the belt have cooperating concave surfaces ofvery slightly smaller concavity, whereby the gaps are narrowest at theedges of the bearing elements.
 3. A conveyor as claimed in claim 1 inwhich the bearing elements are hollow and there is means to supplypressurized fluid to the hollow elements, and thence to the gaps betweenthe bearing elements and the belt.
 4. A conveyor as claimed in claim 3in which there are channels under the hollow elements to catch fluidemitted from the gaps, and there is provision for that fluid to bereturned to the fluid supply means.
 5. A conveyor as claimed in claim 1,in which the fluid is supplied to the gaps through a multiplicity ofcapillaries inset in material adjacent the gaps.
 6. A conveyor asclaimed in claim 1, in which the fluid is supplied to the gaps through amultiplicity of orifices formed in material adjacent the gaps.
 7. Aconveyor as claimed in claim 1 in which the bearing elements formstructural members upholding the belt.
 8. A conveyor as claimed in claim1 in which the material of one of the belt and bearing elements at theedges of the gaps is flexible so to form a seal.
 9. A conveyor asclaimed in claim 1 in which fluid emitted from the gaps serves to eJectforeign material from between the belt and the bearing elements.